Electric switching devices, for example low-voltage circuit breakers in the form of so-called compact switches, known as MCCBs (for molded case circuit breakers) of in the form of so-called open circuit breakers, known as ACBs (for air circuit breakers), break/connect single- or multi-phase current paths by mechanically opening/closing single- or double-breaking/-closing switch contacts. In this context, the switch contacts must be arranged in an electrically insulated manner.
This insulation must be effected both with respect to the installation environment and—in the case of multi-phase electric switching devices—between the individual phases. To achieve this, the parts of the electric switching device which are in each case associated with one such phase of the main circuit and in each case form one switch pole (this includes, in particular, the switch contacts of the respective switch pole) are in each case installed in a separate switching space which is bounded by an insulating enclosure. These insulating enclosures consisting especially of plastic, which also include a large number of rigid housing arrangements differing in their external appearance, at the same time prevent the unrestricted spreading of the gas and particle releases produced during switching processes.
Thus, these insulating enclosures essentially consist, for example in the case of a known housing arrangement, of a housing base, chambered in accordance with the number of switch poles, and an adequate housing top which, as a rule, are joined together by screw connections.
With the application of rotational twin contacts (contact bridges), another housing concept became established in which a switchable, double-breaking contact bridge together with two arc-quenching chambers and possibly still other components needed for each switch pole (slot motor etc.) are arranged in an almost closed cassette consisting in most cases of at least two half shells. These prefabricated single-pole cassettes must then be combined to form switches having the number of poles needed in each case. This combination should be effected whilst maintaining a preferred direction and as few parts as possible and ensuring maximum stability. In this context, the modularity of the individual poles should be maintained.
From the German translation DE 602 11 028 T2 of the European patent specification EP 1 464 063 B1, the entire contents of each of which are incorporated herein by reference, an electric switching device in the form of a low-voltage circuit breaker is known which has such a generic arrangement. In this known arrangement, each of the switch pole housings forms an insulating enclosure of a switching space for accommodating a single switch pole of the electric switching device. In this arrangement, the insulating enclosure has a lower wall, an upper wall, two side walls, a rear wall and a front wall. To provide a joint with other switch pole housings which is reliable with regard to the acting forces and at the same time to avoid complicated joining operations, the at least two switch pole housings are formed of two half shells which rest against one another along a partition joint, the partition joint extending in parallel with the side walls of the switch pole housings. In this arrangement, one of these half shells has on its coupling surface facing the other half shell several hollow pins which protrude transversely from the coupling surface whilst the other one of the two half shells has through-holes correlated with the pins which are suitable for accommodating the hollow pins. In this arrangement, the mutual couplings between the pins and the corresponding holes form insulating ducts which extend transversely through the switch pole housings with respect to the side walls. In this arrangement, the switch poles are connected via clamping and cross-linking elements which extend through the insulating ducts.